Production of aluminum nitrid.



P. R. HERSHMAN.

PRODUCTION OF ALUMINUM NITRID. APPLICATION FILED mac. 22. I9I4.

1,250,874. Patented Dec. 18, 1917;,

R0 fary Furnace Gas Producer 76 I IIWEINTIZLI Mam/2W A TTOHIVEYJ'.

UNITED STATES PATENT OFFICE.

PAUL R. HERSHMAN, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, '10 ARMOUR FERTILIZER WORKS, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW JERSEY.

PRODUCTION OF ALUMINUM NITRID.

Specification of Letters Patent.

Patented Dec. 18,1917.

To all whom it may concern:

Be it known that I, PAUL R. HERSHMAN, a citizen of the Empire of Austro-Hungary, residing in the city of Chicago, county of Cook, State of Illinois, have invented certain new and useful Improvements in Production of Aluminum Nitrid; and I do hereby declare the following to be a full, clear,

and exact description of the invention, such as will enable others skilled in'the art to which it appertains to make and use the same.

My invention relates to the nitrification of aluminiferous materials, by'a furnace operation, wherein the necessary temperature required for the final step of the nitrification is supplied to the furnace charge, either from sensible heat preliminarily imparted to a gas (which may be the nitrifying gas itself), or imparted to the charge partially by combustion of the gas within the furnace chamber. The charge of aluminiferous material may be supplied to the furnace, in the first instance, either in a cold state,'or preheated, as the case may be, and will frequently be supplied at a high temperature, particularly in those instances where the aluminiferous material treated is the direct product of a calcining operation, as, for instance, calcined alunite.

In the accompanying drawing, I have illustrated diagrammatically, a furnace particularly adapted for the purposes of the invention, and which will illustrate its generic character.

Referring to the drawing, A represents any suitable furnace, which may be of the rotary type, as shown, although the practice of the invention is not limited to that type of furnace. The furnace is provided with suitable means for charging it, as well as for subsequently discharging the finished product. For convenience, the interior of the furnace may be subdivided into separate zones or capacities arranged side by side.

The furnace is interposed between two regenerator chambers B, C, adapted to contain a checker-work filling of brick of capacity'to resist, without deterioration, an extremely high heat, that is to say, a heat sufiicient to raise the temperature of the gas or gas mix-' ture employed to the proper point of reaction. Bricks particularly suitable for the purpose, capable of withstanding a temperature even as high as and in excess of 2200 C. are described in an application filed by me of even date herewith. These bricks, which I particularly recommend for the purpose are made by briqueting, preferably with tar or other suitable carbonaceous binder, a mixture of calcined alunite (from which the potash has been removed),and finely divided coke, the coke being present in amount insufficient to convert the entire mass of the calcined alunite into aluminumcarbid during the subsequent heating of the briquet to form the refractory brick.

A gas producer D is provided with a blower E and is designed to furnish the nitrifyinggas for the production of the aluminum nitrid and also the gas for bringing the furnace charge to the nitrifying temperature. Suitable pipes and passages, governedv by controlling reversing valves, are provided to insure the proper conduct of the operation. 7

The furnace A is brought to the required heat by the passage of heated gas through it in one direction and then in the other. Should additional rise in temperature beyond that given by the heated gases be desired, it may be procured by burning a portion of the gas during its passage through the furnace A, as later described.

Referring to the diagrammatic drawing attached to the specification, the blower E is shown forcing air through the valve a into the combustion chamber of the regenerator B. It is also forcing as through the valve 0 into the regenerator a through the checker work of the regenerator, through the furnace A, and into the regenerator B where the hot gas meets the incoming air and combustion takes place, the products of combustion normally passing from the regenerator B through the valve 0 and to the stack.

By closin the valve a, opening the valve 6, closing t e valve 0, opening the valve (1, closing the valve e and opening the valve 7, the course of the gases and air to the regenerators may be changed, etc.

The mixture of alumina and carbon is then admitted intov the furnace. A, the amount of carbon present being in sufiicient excess to insure the complete reduction of the alumina. The alumina thus admitted may be, for instance, calcined alunite hot from the heat of calcination or, preferably calcined alunite which has been raised to such a high t mperature as will have suiiiced to drive off by volatilization most of its residual alkali content and such other foreign bodies as may be subject to volatilization at feasible temperatures. The car bon being admit-ted into the rotary furnace either before or after the admission of the highly heated body of alumina, or in admixture with the alumina, a few turns of the to a temperature much higher than the temperature of the charge in the furnace, so that the temperature of the charge rises gradually by reason of the sensible heat imparted to it from the producer gas; or the rise in temperature of the charge may be further assisted by burning a part of the gas within the furnace chamber A by the admission of a quantity of air thereto through the valve Z thereby adding heat of combustion to the sensible heat of the gas.

It wiil be apparent that the charge may thus be brought to the nitrifying temperature either by producer gas or any other suitable gas, as, for instance, carbon monoXid. In any event, however, when the nitrifying temperature'is reached, a suitable supply of a nitrifying gas must be available for the charge at the proper temperature and, for this reason it is preferred to bring the charge up to the nitrifying temperature by the use of producer gas because it is not only a heating gas but also a nitrogen carrier, and may therefore enter upon its nitrifying function immediately that the appropriate temperature conditions are produced in the furnace charge. The gas, after passing through the furnace A, is burned in the rcgenerator B by air supplied from the blower, whereupon the refractory bricks in the regenera'tor chamber B are correspondingly heated to an increased temperature. As will be readily un-- derstood, when the temperature in the regenerator chamber C has fallen below the limit required for maintaining nitrifying conditions in the charge of the furnace A, .1. suitable reversal of the valves is effected, whereupon the gas is caused to pass through the regenerator chamber B and thence through the furnace A, and is thereupon burned in the regenerator chamber C to restore to the bricks of that chamber the heat which they have just parted with.

Provision is made, as indica ed, for taking in cold air from the outer atmosphere into the blower through the valve g or for returning a part of the products of combustion through the valves h and 2, to the blower and thence into the producer, if it should be desired to thus re-utilize in the producer itself, a portion of the heat of the products of combustion after they have passed through the regenerator chambers.

From the foregoing description, it will be recognized that the temperature necessary for maintaining nitrifying conditions within the furnace A is supplied either from the heat imparted to the gas by the regenerator bricks (which can be brought to a temperature several hundred degrees higher than is required for nitrification, and, indeed, to a temperature as high as 2200 C. and above) or by auxiliary heat due to a partial combustion of the gas in the furnace A. With bricks of a heat-resistivity sufficient to withstand as high'a temperature as 2200 C. and above, the reversals of the course of the gas through the two regenerator chambers may be made at intervals suiiiciently far apart to allow a considerable drop in tem perature in the regenerator chamber through which the gas is passing before it is necessary to reheat the bricks of that chamber. In other words, the large excess of available heat beyond that necessary for sustaining the nitrifying temperature in the furnace A is made available to maintain Working conditions in the furnace A Without too frequent a reversal, of the valves.

It may be further pointed out that in passing through the furnace A, the producer gas not only gives up nitrogen to form aluminum nitrid, but also takes on a correspondlng quantity of carbon monoxid,

so that its capacity to heat the regenerator chambers when ignited and burned therein is correspondingly raised, to the advantage of the general operation. If desired, such small quantities of Water-vapor as are contained in the producer gas may be abstracted therefrom by condensation, and such quantities of carbon dioxid as are present therein may be absorbed by passing the gas into contact with calcium oXid or the like, on its passage to the generator; but, for" general uses, the amount of Water-vapor and of carbon dioXid in the producer gas is not sufiicient to introduce any materially disturbing condition in the operation that would justify the expense of removing either of them from the gas.

The practice of the invention is of particular advantage for a number of reasons that will readily be appreciated. In the first place, the high temperatures realized are obtained as the result of gas production and combustion, secondly, the nitrogen, which is normally inert is made particularly active because of the high temperature to Which Hit) it is raised, in excess of that required for nitrification of the aluminiferous material, and which, moreover, enables it to impart heat to the charge instead of abstracting it therefrom; and thirdly, because of the relatively enormous volume of nitrogen which can thus be poured through the charge in excess of that theoretically required for its nitrification, places at the disposal of the operator a supply of nitrogen constantly maintained and far beyond the needs of the charge, so that the benefit of mass action is present as an important factor in the completeness and speed of the reaction.

What I claim is 1. The method of nitriiifying a furnace charge containing alumini erous material,

which comprises raising the charge to the nitrification point by passing through the charge-containing chamber, in the presence of the charge, a gas. preliminarily heated to a high temperature, burning a portion of the gas in the presence of the charge, and nitrifying the charge; substantially as described.

2. The method of nitrifying a furnace charge containing aluminiferous material, which comprises raising the charge to the nitrification point by passing through the charge-containing chamber, in the presence of the charge producer gas preliminarily heated to a high temperature, burning a portion of the gas 'in the presence of the charge, and nitrifying the charge by continuing the passage of producer gas through the chamber in the presence of the charge, substantially as described.

In testimony whereof I aflix my signature, in presence of two Witnesses.

PAUL R. HERSHMAN.

Witnesses:

M. Ame, M. A. BILL. 

